A giant magnetoresistance (GMR) element formed by a multi-layer film including a ferromagnetic layer and a non-magnetic layer and a tunneling magnetoresistance (TMR) element using an insulating layer (a tunnel barrier layer, a barrier layer) as a non-magnetic layer are known. In general, the TMR element has a higher element resistance than the GMR element, but the TMR element has a higher magnetoresistance (MR) ratio than the GMR element. For that reason, the TMR element has gained attention as elements for magnetic sensors, high-frequency components, magnetic heads, and non-volatile random access memories (MRAM).
The MRAM reads and writes data by using a characteristic in which the element resistance of the TMR element changes when the mutual magnetization directions of two ferromagnetic layers sandwiching an insulating layer change. As a writing method of the MRAM, a method of performing writing (magnetization reversal) by using a magnetic field caused by a current and a method of performing writing (magnetization reversal) by using a spin transfer torque (STT), which is generated by a current flowing in a lamination direction of the magnetoresistance element, have been known. The magnetization reversal of the TMR element using STT is efficient from the viewpoint of energy efficiency, but a reversal current density for the magnetization reversal is high. From the viewpoint of the long lifetime of the TMR element, it is desirable that the reversal current density be low. The same applies to the GMR element.
In recent years, as a means for reducing the reversal current by a mechanism different from the STT, magnetization reversal using a pure spin current generated by a spin hall effect has gained attention (for example, see Non-Patent Document 1). The pure spin current generated by the spin hall effect induces a spin-orbit torque (SOT) and magnetization reversal occurs by the SOT. Alternatively, even in the pure spin current caused by the Rashba effect at an interface of different materials, the magnetization reversal is caused by the same SOT. The pure spin current is generated when the same number of upward spin electrons and downward spin electrons flows in the opposite directions and the flows of electric charges are cancelled. For that reason, since the current flowing in the magnetoresistance effect element is zero, there has been an expectation of realizing the magnetoresistance effect element having a small reversal current density.
The spin hall effect is dependent on the magnitude of the spin-orbit interaction. In Non-Patent Document 2, Ta which is heavy metal having d electrons causing a spin-orbit interaction is used in the spin-orbit torque wiring. Further, it is known that spin-orbit interaction occurs due to an electric field inside a crystal caused by the collapse of spatial inversion symmetry in GaAs which is a semiconductor.